Study of the Effect of the Unified Power Flow Control System on the Performance of the Distance Relay Used in the Transmission line

Abstract

Flexible Alternating Current Transmission devices (FACTs) have recently been widely used in transmission lines with the aim of improving the flow of

electric power and improving the stability of the electric power system and its various and many advantages, but its presence in transmission lines has led to some challenges related to the work of protection system devices, where the distance relay plays an important role in transmission lines Transmission as part of the protection system that must be taken into account, the presence of FACTs devices causes a change in the impedance measured by the distance relay, which can cause improper transmission line disconnection or improper operation of the relay, as it is known that the wrong performance of protection systems, It can lead to even electrical network problems Complete blackout, with its negative consequences for consumers and the country's economy, therefore it resulted in analyzing the performance and studying the impact of these devices on the work of the distance relay under various circumstances and conditions.

The aim of this work is to study the effect of the UPFC Unified Power Flow Control device used to improve the stability of the electric power system,where in the Matlab/Simulink program environment, the distance relay, the unified power flow control device, and the transmission line were simulated, and the case of a fault on the transmission line was studied and the performance of the relay  was evaluated.

The results showed a change in the visible measured impedance by the distance relay, and thus the possibility of unreliable operation of the distance relay in the presence of such devices unless taken into account in advance in the calibration stage of the distance relay.